This invention relates to a power transmission belt and method for fabricating the same, and particularly relates to a power transmission belt such as a V-ribbed belt or a V-belt including short fibers mixed into its compression rubber and a method for fabricating the same.
As disclosed in, for example, Japanese Patent Application Laid-Open Gazette No. 3-219147, there are conventionally known power transmission belts in which a crowd of short fibers are mixed into their compression rubber in a manner to be oriented along the width of the belt and some of the short fibers are extruded from the surface of the compression rubber. Power transmission belts of such kind aim at enhancing bearing strengths and wearing properties of their friction drive sections and preventing noise production during their running.
However, even such a power transmission belt out of which some of the short fibers extrude, if the total area of extruded sections of the short fibers occupying the surface of the compression rubber is small, cannot enhance its wearing property so much because the area of the compression rubber in direct contact with a pulley becomes correspondingly large.
For the purpose of increasing the exposure areas of short fibers, the power transmission belt disclosed in the above gazette has proposed to set the process temperature in grinding at a higher temperature so as to melt tips of short fibers by heat produced in grinding. In this manner, as shown in FIG. 17, an exposure section 101 of each short fiber 100 is formed as if a flower blooms, resulting in increased exposure area of the short fiber 100.
However, when melted, a short fiber changes its molecular structure and therefore deteriorates its strength. Accordingly, though the above conventional power transmission belt is increased in exposure area, it is difficult to say that the belt is sufficiently enhanced in wearing property.
Furthermore, if the length for which the short fiber is extruded from the surface of the compression rubber is too large in order to increase the exposure area, the belt will largely change its properties when the extruded sections of the short fibers are reduced by abrasion. Therefore, considering to maintain desired belt properties constant for a long time, there is a limit to increasing the extruded length of the short fiber. Accordingly, it has been desired to make great strides in enhancing the performance of the belt by improving not only short fibers but also the compression rubber.
In view of these problems, an object of the present invention is to enhance the wearing property of the belt by increasing the exposure area of each short fiber while ensuring the strength of thereof.
Another object of the present invention is to further enhance the performance of the belt by improving the surface configuration of the compression rubber.
To attain the above first object, a power transmission belt of the present invention is constructed so that short fibers are plastically deformed into flat form.
More specifically, a power transmission belt of the present invention is directed to a power transmission belt in which a crowd of short fibers are mixed into a compression rubber there of in a manner to be oriented in a given direction and some of the short fibers each have an extruded section extruded from a surface of the compression rubber, and is characterized in that the extruded section of the short fiber is formed into flat shape by plastic deformation.
With this construction, since the extruded section of the short fiber is not melted, it can retain intrinsic strength. Furthermore, since the extruded section of the short fiber is plastically deformed by an external force into flat form, it has a larger exposure area than that of circular cross section. As a result, the belt can enhance wearing property. Thus, since the extruded section of the short fiber is formed into flat shape by plastic deformation, it can retain intrinsic strength and ensure a large exposure area, resulting in enhanced wearing property of the belt.
The extruded section of the short fiber is preferably formed in a sector gradually broadened toward a distal end thereof.
With this construction, the extruded section of the short fiber can obtain a specific flat configuration of large exposure area.
Meanwhile, in the above conventional belt, since the extruded short fibers are easy to fall to the surface of the compression rubber, they are difficult to together form surface unevenness as considered as effectively suppressing noise. Therefore, the conventional belt is likely to produce noise.
To cope with this problem, the extruded sections of the short fibers are preferably raised at root portions thereof from the surface of the compression rubber. With this construction, microscopic unevenness is formed over the surface of the compression rubber so that the raised root portion of each extruded section constitutes a microscopic convexity and a rubber surface region adjoining a place where each extruded short fiber is implanted in the compression rubber constitutes a microscopic concavity, thereby suppressing the occurrence of noise.
The short fiber is preferably formed of a synthetic fiber with a filament diameter of20 xcexcm or more. This provides a suitable short fiber for exerting the above effect of suppressing noise.
To attain the above second object, a power transmission belt of the invention is constructed so that unevenness is provided in the surface of the compression rubber to increase its entire surface area.
Specifically, in the power transmission belt, the surface of the compression rubber is preferably formed in uneven configuration.
With this construction, since the surface of the compression rubber is formed unevenly, its entire surface area can be increased. This enhances the performance of the belt. In addition, clearances are likely to be formed between contact surfaces of the belt and a pulley. Accordingly, even if water or the like enters between the belt and pulley, it can be distributed or discharged through the clearances, which stabilizes the frictional resistance of the belt.
The surface unevenness of the compression rubber is preferably formed in wavy shape. Thereby, a suitable uneven configuration can be formed in the surface of the compression rubber.
The surface unevenness of the compression rubber is preferably formed to have a level difference of 0.5 to 10 xcexcm. Also in this case, a suitable uneven configuration can be formed in the surface of the compression rubber.
A method for fabricating a power transmission belt of the present invention is directed to a method for fabricating a power transmission belt in which some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives extruded for 50 to 95% in grain size thereof from the surface of the grinding wheel.
According to this method, the extruded non-aramid synthetic fibers are inclined in a grinding direction by interference with the super abrasives and then plastically deformed one after another, as they are released from stresses induced in their surfaces by interference with the super abrasives, so as to be bowed and formed into flat shape as gradually broadened toward their distal ends while being partly pulled apart at their distal ends. Further, since the height of extrusion of each of the super abrasives is large, a bonding part for the super abrasives in the grinding wheel is prevented from direct contact with the compression rubber of the power transmission belt, there by suppressing production of frictional heat. Therefore, the extruded sections of the non-aramid synthetic fibers are not heated so much during grinding so as to be prevented from being melted. In other words, it can be facilitated to plastically deform the non-aramid synthetic fibers and extrude them from the surface of the compression rubber while keeping them unmelted. Accordingly, a power transmission belt in which extruded sections of non-aramid synthetic fibers are plastically deformed can be easily obtained. In addition, such a large height of extrusion of the super abrasive can facilitate to form the surface of the compression rubber into uneven configuration.
Another method for fabricating a power transmission belt of the present invention is also directed to a method for fabricating a power transmission belt in which some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives the density of which is 3.5 to 55%.
According to this method, since the density of the super abrasives is small, chip pockets can be increased so that grinding chips can be readily expelled. Therefore, clogging between the abrasives due to the chips is difficult to occur. This suppresses heat production during grinding. Accordingly, a power transmission belt in which extruded sections of non-aramid synthetic fibers are kept unmelted and plastically deformed can be easily obtained. In other words, it can be facilitated to plastically deform the non-aramid synthetic fibers and extrude them from the surface of the compression rubber while keeping them unmelted. In addition, such a small density of the super abrasives can facilitate to form the surface of the compression rubber into uneven configuration.
Still another method for fabricating a power transmission belt of the present invention is also directed to a method for fabricating a power transmission belt in which some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives which are each extruded for 50 to 95% of grain size thereof from the surface of the grinding wheel and the density of which is 3.5 to 55%.
According to this method, since the height of extrusion of each of the super abrasives is large, a bonding part for the super abrasives in the grinding wheel is prevented from direct contact with the compression rubber of the power transmission belt, there by suppressing production of frictional heat. Further, since the density of the super abrasives is small, chip pockets are large in size so that grinding chips can be readily expelled. Therefore, clogging between the abrasives due to the chips is prevented. This suppresses heat production during grinding. Accordingly, a power transmission belt in which extruded sections of non-aramid synthetic fibers are kept unmelted and plastically deformed can be easily obtained. In other words, it can be facilitated to plastically deform the non-aramid synthetic fibers and extrude them from the surface of the compression rubber while keeping them unmelted. In addition, it can be facilitated to form the surface of the compression rubber into uneven configuration.